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Wednesday, July 25, 2007

5/13/2007: More About Stem Cell Transplants

Many of my friends and family have asked about stem cell transplant procedures, so here is some information gathered from THE LEUKEMIA & LYMPHOMA SOCIETY website:

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"Obtaining marrow stem cells for transplantation requires that an appropriate donor receives a thorough health examination, which includes an electrocardiogram, chest x-ray, blood chemistry evaluation, and confirmation that blood cell counts are normal.

The donor is tested to insure that hepatitis viruses and human immunodeficiency virus (HIV) are not present in the blood. The presence of a positive test for cytomegalovirus (CMV) does not necessarily prevent a person frombeing a donor."

Marrow donation is a surgical procedure. The donor is given anesthesia in an operating room suite. The transplant physicians use a special hollow needle attached to a large syringe to withdraw samples of marrow from the top edge of the pelvic bones. This area can be easily felt under the skin of the sides and back just below the waist. The insertion of the needle through the skin and into the rim of the pelvic bone is repeated until several pints of marrow are removed. The donor usually remains in the hospital for about 12 hours before going home. During this time, the donor recovers from both the anesthesia and the pain at the needle insertion sites.

The donor can expect to feel some soreness in the lower back for a few days or longer. Most donors are back to their normal routine in a few days. Marrow is completely replaced within 4to 6 weeks following donation."

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A few other facts that I have gathered include:

Transplant physicians can test to determine the degree of compatibility before a decision is made to use the donor. Compatibility is assessed by laboratory tests that identify the tissue type of donor and recipient. There are two types of allogeneic donors:

• Related allogeneic donors, usually sibling donors

• Unrelated allogeneic donors, usually found within very large pools of volunteers, and matched to a tissue type that is the same as the patient’s.

Transplantation from a matched unrelated donor is sometimes referred to as “MUD” transplant.

Both related and unrelated allogeneic transplantation differs from either syngeneic or autologous transplantation in that the following may occur:

• The immune rejection of the donated stem cells by the recipient (host versus graft effect).

• The immune reaction by the donor’s cells against the tissues of the recipient (graft versus host disease)

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If I am to obtain a transplant from an unrelated donor, then ...A) The donor will likely be youngerB) Same genderC) Have my same blood type, A+

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TESTING TO IDENTIFY DONORS

"When a transplant is under consideration, the patient and his or her siblings will be tested to determine their tissue type or human leukocyte antigen (HLA) type.

"The tissue type of an individual is determined by proteins on the surface of cells.

"Like other tissue cells, the leukocytes (white cells) contain these surface proteins. By testing the leukocytes obtained from a blood sample, transplant physicians can determine the HLA type of the patient and potential donors. The immune reactions that occur when nonidentical individuals receive a transplant are governed largely by these cell surface proteins. The lymphocytes of the recipient can sense that the donor’s cells are “foreign” and attempt to kill (reject) them. The donor’s immune cells can sense that the patient’s cells are “foreign” and attack them.

"The degree of difference in tissue type between donor and recipient is the main determinant of the intensity of:

These two reactions do not happen if the recipient and donor are identical twins."However, the fact that these reactions do happen in nonidentical siblings, even if they are matched by tissue typing, shows that HLA testing does not examine all relevant tissue type factors. In light of this fact, two processes are necessary to permit a successful transplant: suppression of the recipient’s immune system before transplant and suppression of the donor’s immune cells in the recipient after transplant."Reference:"Blood and Marrow Stem Cell Transplantation"The Leukemia & Lymphoma Society